Google Earth and Geoscience Education

Peter Selkin, University of Washington, Tacoma

Introduction: What is Google Earth

Google Earth is a virtual globe browser, arguably the most popular of those available for free on the Internet (NASA's World Wind (more info) and ESRI's upcoming ArcGIS Explorer are competitors). Virtual globes allow users to interactively display and investigate geographic data (primarily satellite and aerial images and terrain models, but also 2- and 3-D vector data such as earthquake locations, water bodies, and buildings). One of the most useful aspects of Google Earth from a geoscience education point of view is the availability of a variety of geoscience-related datasets for free on the web.

Google Earth allows users to perform some basic measurements (latitude and longitude, elevation, and size), which has led some users to consider it a variety of GIS software. Geoscience professors should be careful when making this comparison. Alan Glennon, a graduate student in geography at UCSB, wrote two essays on the pros and cons of so-called "naive" GIS (mainly focusing on applications such as Google Earth). The essays (and the comments on them by other geographers) are a good starting point if you are trying to decide whether to use a virtual globe such as Google Earth or a full-featured GIS such as ArcGIS or GRASS in the classroom. (also see Glenn Richard's Google Earth or GIS? section from the SERC Teaching with Google Earth website.

How to Obtain a Copy

The Google Earth browser is a separate application from your web browser. As of July 16, 2006, the current stable version (v.3) runs on both Windows 2000/XP and Mac OSX (10.3.9 and higher). A beta version (v.4) runs on Windows, Mac OSX, and Linux platforms. The Google Earth browser can be downloaded from http://earth.google.com/ (more info) .

Several upgrades to the Google Earth software are available. This discussion covers the standard version (available for free for personal or educational use). I do not have experience with the "plus" ($20) or "pro" ($200+) upgrades.

Using Google Earth

Getting Around in Google Earth: Common Functions

Navigation in Google Earth will be fairly intuitive for students who have grown up in an age of clicking and dragging, mouse wheels, and video games. Those who are not familiar with the interface may wish to take a look at one of the guides in the text box below. These guides describe the basics of browsing in Google Earth better than I can. Nonetheles, I will summarize some of the basics here.

Google Earth allows the user to view true-color images draped over topography for most of the globe, at varying resolutions mainly depending on the browser's "eye altitude" (height above ground). The user can navigate (pan) either by clicking and dragging part of the field of view with the mouse, by using the arrow keys, or by using a set of navigation arrows displayed in the main Google Earth viewer window. The window's viewpoint can be rotated relative to the virtual globe using a sliding or rotating control on the viewer window. The viewpoint can zoom into the globe using a slider control, the mouse wheel (PC) or control-clicking and dragging (Mac). The viewpoint can also "tilt" from a vertical position to a nearly horizontal poisition (again using a slider control).

Google Earth's main attraction, however, has been its ability to display vector datasets (placemarks - points, lines, and polygonal areas), raster images (overlays), and 3D virtual models on top of the virtual globe. Although some placemarks and overlays are supplied with Google Earth or are directly accessible through Google Earth in the "Google Earth Community", the majority must be downloaded from the Web. Placemarks and overlays are discussed in more detail later.

3D models of buildings in some cities are provided with Google Earth (the "Buildings" layer), but to get the most use out of 3D models, you will have to download the SketchUp plugin. This will allow you to build and use 3D objects in Google Earth. Although 3D models are fun to play with, they are less broadly useful than other types of placemarks, so I won't go into them in detail. One clever use of 3D models in an educational context, however - an exercise on visualizing wind farms - is from Noel Jenkins' Juicy Geography site.

You and your students will probably find it useful to be able to measure features in Google Earth. Here are a few hints on how to make a couple of different measurements:

• Position: The latitude and longitude of the mouse pointer are shown in the status bar near the bottom of the screen. An option in the Preferences dialog box allows you to change whether position is displayed in degrees-minutes-seconds format or decimal degrees.
• Elevation: The elevation of the mouse pointer is also listed at the bottom of the screen. The "eye alt" value is the elevation of your viewpoint. An option in the Preferences dialog box allows you to change whether elevation is displayed in feet or meters.
• Distances: Google Earth allows you to measure the great circle distance from one point to another or along a path (through several points), Distances are measured as the crow flies, without taking topography into account (as far as I can tell). In Google Earth 3, the measurement tool is found under the "Tools" menu. In Google Earth 4, the measurement icon appears as a ruler at the top of the window.
• Vertical exaggeration can also be changed in the Preferences dialog box.

One final note about Google Earth navigation: The top panel on the left side of the Google Earth window ("Search") allows the user to search for a location. In my experience, the search function is not perfect: a search for Augustine Volcano, for example, returns no results, and a search for "Mount Rainier" after a search for "Tacoma, WA" returns local businesses with the word "Rainier" in their names. Latitude and longitude can be used instead of a place name for less ambiguous searching.

Placemarks and Overlays

As mentioned above, one of the most appealing aspects of Google Earth is the ability to import and plot information on top of the virtual globe. Placemarks and overlays are distributed as KML (Keyhole Markup Language) or KMZ (compressed KML) files, which can be opened (by selecting Open from the File menu) in Google Earth. KML/KMZ files (I'll refer to both as KML) can be opened in either version of Google Earth.

After you open a KML file, it shows up in your Google Earth browser in two ways:

• In the main window, the file shows up as placemarks (dots or icons, lines, or polygonal areas) or overlay images. Clicking on the icon of a placemark in the browser window will cause a small window to pop up. These popup windows typically show more information about the placemark (a description of a volcano, a photograph, a web link, etc.).
• In the "Places" pane (middle of the left side of the Google Earth window), you may notice the names of your placemarks or placemark collections. Clicking on the name of a placemark will zoom into that placemark in the browser window. Otherwise, the Places windowpane is similar to the Table of Contents in ESRI's ArcGIS products, or the Folders pane in Microsoft's Windows Explorer. Clicking on the triangles next to the names of placemark collections or folders will list the contents of the collection.

Some placemarks or placemark collections are dynamic, in that they contain information that changes through time. For example, the USGS has a placemark collection that shows all earthquakes that have occurred over the past 7 days. Obviously this will change as time goes by - earthquakes that occurred more than 7 days ago will be dropped from the list, and new ones will be added. The placemark collections from the USGS automatically update the list of earthquakes once you have downloaded and opened the KML file. Dynamic placemarks or collections are called network links in the Google Earth lingo.

You can make your own KML files: see below.

Using Google Earth in Geoscience Education

Here are a few general suggestions for ways you might be able to incorporate Google Earth into your Earth Science classroom:

• Topographic map interpretation: using GPSVisualizer , you can create topographic map overlays, which can be viewed at different angles (and different vertical exaggerations) in Google Earth. This could supplement the plastic topo map models that many classrooms have. I sometimes show my students pictures of a location, and try to have them determine from a topographic map where the photo was taken - I can imagine doing this with GE, GPSVisualizer, and Panoramio (or a similar set of tools). If you need better terrain models than Google Earth's SRTM topography, you might check out the KML Exporter for SceneExpress , for use with LIDAR, etc.
• Measurement: Google Earth's tools could allow students to collect quantitative data by measuring elevations, distances or areas. For example, students could measure and compare the relative sizes of basaltic versus andesitic volcanoes (with caveats of course!), or could determine plate velocities from ocean island - hotspot distances (again, with some discussion of the pitfalls...).
• Decision-making: Students could use placemarks and overlays to explore the use of geographic data in decision-making (e.g. where to site a nuclear plant, a dump, or a wind farm ). In this respect, Google Earth is not quite as good as a full-featured GIS, since you can't ask it, for example, "which dump sites are in a different watershed from our drinking water source?" However, for most introductory students, Google Earth's features will be sufficient to make some conclusions.
• Field trips: Although the idea of virtual field trips has been around for a while, Google Earth (and its cousin Google Maps ) has the potential to greatly improve real field trips - giving students a preview of trip locations, overlaying other data on top of scenery, and (most exciting from my point of view) the ability to share field trip sites with other instructors....
• Visualizing Abstract Phenomena: Google Earth's overlays and SketchUp models should allow you to make thematic maps (in 3D!) of hard-to-grasp features such as gravity, magnetic anomalies, or EM survey data. Here's an example of an electromagnetic survey disguised as art . It's a man-made feature rather than something geological, but it illustrates the concept. I'm imagining something like gravity surveys overlain on top of this region ( 667bytes Oct5 06) in the Gulf of Mexico....

Keyhole Markup Language (KML): Building Placemarks and Overlays by Hand

If you are intrested in creating your own placemarks but are daunted by the possibility of having to pay for GE Pro, do not fear! The free version of GE does allow you to produce placemarks and overlays (the latter is true in the Mac version; I am not sure about the Windows version). There are a number of tutorials on making placemarks (KoKae Screencasts ( This site may be offline. ) has a good one from February 23, 2006), which can be accomplished with the click of a button in all versions of Google Earth.

Looking under the hood of placemarks and overlays is not difficult - KML files are essentially text files and can be edited in a text editor. If you want to build your own placemarks and overlays, it is useful to be able to edit the KML manually. This way you can make lines of different colors, add annotation, etc. The Google KML tutorial is here . The tutorial is written for KML version 2.0; version 2.1 is currently being beta-tested. Documentation for the two versions is here: 2.0 , 2.1 .

Collaborative editing (usually in the form of wikis ) has become one of the buzzwords in the Web world of late. You can make collaborative placemark collections using the EditGrid online spreadsheet: here 's how from Alan Glennon, UCSB. Also from Alan Glennon: collaborative placemarking by email . And another idea, this time from disaster relief collaboration Strong Angel III: collaborative placemarking by SMS (text messaging from cell phones).

Finally, if you want to make your Google Earth placemarks more widely usable, you can incorporate them into Google Maps. They can then be viewed directly in a Web browser using the Google Maps interface.